| Abstract
| - The adsorption of water (D2O) molecules on Rh(111) at 20 K was investigated using infrared reflectionabsorption spectroscopy (IRAS). At the initial stage of adsorption, water molecules exist as monomers onRh(111). With increasing water coverage, monomers aggregate into dimers, larger clusters (n = 3−6), andtwo-dimensional (2D) islands. Further exposure of water molecules leads to the formation of three-dimensional(3D) water islands and finally to a bulk amorphous ice layer. Upon heating, the monomer and dimer speciesthermally migrate on the surface and aggregate to form larger clusters and 2D islands. Based on the temperaturedependence of OD stretching peaks, we succeeded in distinguishing water molecules inside 2D islands fromthose at the edge of 2D islands. From the comparison with the previous vibrational spectra of water clusterson other metal surfaces, we conclude that the number of water molecules at the edge of 2D islands is comparablewith that of water molecules inside 2D islands on the Rh(111) surface at 20 K. This indicates that the surfacemigration of water molecules on Rh(111) is hindered as compared with the cases on Pt(111) and Ni(111) andthus the size of 2D islands on Rh(111) is relatively small.
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